Tisa Silver-Canady realized toward the end of last year that she had not used about a third of her vacation time.

Last year, the financial aid administrator at the University of Maryland-Baltimore took two brief trips -- one for work, the other a vacation that included a job-related conference. And she took two days off to move to a new house.

But she got busy at work with deadlines. "I didn't have any huge plans, so I thought, 'Why waste it?'" Silver-Canady said. "You think about those emergencies and those what-ifs, and something is telling you to hold on just in case."

Breaking away from work to take vacation can be one of the toughest parts of the job for many employees. That's one reason most workers didn't take all the time they had coming last year, according to one survey. A whopping 70 percent of employees polled by Right Management in November and December said they did not take all the vacation due them in 2012.

A survey last year by Expedia showed that Americans earn fewer vacation days than workers in most countries -- 12 days on average -- but still leave two days unused. The trend, which became more prevalent during the recession, appears to be spilling over into the recovery.

When companies were laying off people in greater numbers and requiring more of fewer workers, many workers were reluctant or unable to take time off, said Katherine Ponds, a regional vice president for Right Management, a subsidiary of ManpowerGroup, based in Milwaukee.

Ponds noted that the percentage of employees who failed to take all of their vacation did not decrease from the prior year's survey.

"It appears that more and more people are just simply not placing vacation as a priority, and it does suggest this might become more of the norm," Ponds said. "With so much emphasis on work and on achieving results, many employees are putting that above their personal needs and not recognizing and appreciating the fact that vacation can indeed have a very positive impact on their professional performance."

The top reasons workers cited for not using vacation were not being able to afford one, wanting to save time for future trips, and having difficulty coordinating time off with family members' schedules, the Expedia survey showed. Others said they feared important work decisions would be made without them or that taking all of their time would be perceived negatively by an employer.

Nothing in Right Management's survey results suggested that managers are discouraging employees from taking vacation, Ponds said. "We think that the disconnect that may be occurring is that many employees do have much more that they are accountable for in terms of their work and may fail to appreciate that's even more of a reason to take vacation," Ponds said.

Some employers said they offer vacation benefits to give employees time away from the job and encourage them to use it. Some said they allow vacation days to be carried over and banked from year to year, while others have a use-it-or-lose-it policy.

Tom Filippini, CEO of NextGreatPlace Inc., a membership-based online vacation shopping service, said several employers in the Denver area recently joined NextGreatPlace to offer the services to their workers.

Filippini said millions of vacation days go unused every year. He heard from companies that "employees are not using vacation time. They don't know where to start on the Internet. They get overwhelmed and throw their hands up and end up not using it."

But employers, including some who have become attracted to the service, "are beginning to recognize if employees are not taking vacation, their performance suffers," Filippini said. "In some cases, there's a correlation between the lack of vacation and health issues. Employers are looking for ways to help employees get out of the office."

Aiming to jolt the rest of the world to action, President Barack Obama moved ahead Sunday with even tougher greenhouse gas cuts on American power plants, setting up a certain confrontation in the courts with energy producers and Republican-led states.